45,539 research outputs found
Middle Atmosphere Program. Handbook for MAP. Volume 16: Atmospheric Structure and Its Variation in the Region 20 to 120 Km. Draft of a New Reference Middle Atmosphere
A draft of a new reference atmosphere for the region between 20 and 80 km which depends largely on recent satellite experiments covering the globe from 80 deg S to 80 deg N is given. A separate international tropical reference atmosphere is given, as well as reference ozone models for the middle atmosphere
Galaxy population properties in the rich clusters MS0839.8+2938, 1224.7+2007 and 1231.3+1542
This paper discusses the galaxy populations of three rich clusters, with
redshift 0.19 (0839+29), 0.24 (1231+15), and 0.32 (1224+20), from the database
of the CNOC1 consortium. The data consist of spectra of 52 cluster members for
0839+29, 30 members for 1224+15, and 82 members for 1231+15, and there are
comparable numbers of field galaxy spectra. 0839+29 is compact with no strong
radial gradients, and possibly dusty. 1224+20 is isolated in redshift, has low
velocity dispersion around the cD galaxy, and low 4000A break. 1231+15 is
asymmetrical and we discuss the possibility that it may be a recent merger of
two old clusters. We find few galaxies in 0839+29 and 1231+15 with ongoing or
recently truncated star-formation.Comment: 16 pages and 20 diagrams, to appear in A
Real-time flutter analysis of an active flutter-suppression system on a remotely piloted research aircraft
Flight flutter-test results of the first aeroelastic research wing (ARW-1) of NASA's drones for aerodynamic and structural testing program are presented. The flight-test operation and the implementation of the active flutter-suppression system are described as well as the software techniques used to obtain real-time damping estimates and the actual flutter testing procedure. Real-time analysis of fast-frequency aileron excitation sweeps provided reliable damping estimates. The open-loop flutter boundary was well defined at two altitudes; a maximum Mach number of 0.91 was obtained. Both open-loop and closed-loop data were of exceptionally high quality. Although the flutter-suppression system provided augmented damping at speeds below the flutter boundary, an error in the implementation of the system resulted in the system being less stable than predicted. The vehicle encountered system-on flutter shortly after crossing the open-loop flutter boundary on the third flight and was lost. The aircraft was rebuilt. Changes made in real-time test techniques are included
Nationwide forestry applications program. Ten-Ecosystem Study (TES) site 6, Fort Yukon, Alaska
The author has identified the following significant results. Analysis of the processing results has led to the following conclusions: (1) LANDSAT imagery was a reliable resource for the stratification of level 2 forest features (softwood, hardwood, tundra, and water). These features can be classified with an accuracy of 72.4 percent + or - 5.9 percent at the 90 percent confidence level. (2) Training fields selected for signature development from only 10 percent of the area did not adequately and efficiently cover the class variability for the entire area. (3) Derived regression transformations were ineffective in recovering the loss of level 1 forest proportions and level 2 softwood and hardwood proportions
Computer integration of hydrodynamics equations for heat pipes
Program has five operational modes that provide user flexibility in answering crucial heat-pipe design questions. User specifies heat input and rejection distribution
Mobile terminal equipment design utilising split-loop phase-lock techniques
The design and resultant performance of the terminal equipment in a mobile satellite system is vitally important in respect to the overall cost/performance compromise of the whole system. Improvements in system performance which also result in a reduction of the equipment cost are rare. However, this paper details a significant advance in terminal design, utilizing a novel form of 'split-loop' phase locked receiver/downconverter system to enable an accurate, stable and wide coverage terminal to be realized at a reduced cost. The system has the capability of automatically locking onto any carrier within a complete transponder, and can cope with severe amplitude modulation and fading effects
Overview of crew member energy expenditure during Shuttle Flight 61-8 EASE/ACCESS task performance
The energy expenditure of the Shuttle Flight 61-B crewmembers during the extravehicular performance of Experimental Assembly of Structures in EVA (EASE) and Assembly Concept of Construction of Space Structures (ACCESS) construction system tasks are reported. These data consist of metabolic rate time profiles correlated with specific EASE and ACCESS tasks and crew comments. Average extravehicular activity metabolic rates are computed and compared with those reported from previous Apollo, Shylab, and Shuttle flights. These data reflect total energy expenditure and not that of individual muscle groups such as hand and forearm. When correlated with specific EVA tasks and subtasks, the metabolic profile data is expected to be useful in planning future EVA protocols. For example, after experiencing high work rates and apparent overheating during some Gemini EVAs, it was found useful to carefully monitor work rates in subsequent flights to assess the adequacy of cooling garments and as an aid to preplanning EVA procedures. This presentation is represented by graphs and charts
Statistical comparison of pooled nitrogen washout data of various altitude decompression response groups
This analysis was done to determine whether various decompression response groups could be characterized by the pooled nitrogen (N2) washout profiles of the group members, pooling individual washout profiles provided a smooth time dependent function of means representative of the decompression response group. No statistically significant differences were detected. The statistical comparisons of the profiles were performed by means of univariate weighted t-test at each 5 minute profile point, and with levels of significance of 5 and 10 percent. The estimated powers of the tests (i.e., probabilities) to detect the observed differences in the pooled profiles were of the order of 8 to 30 percent
Normalised Root Mean Square and Amplitude of Sidebands of Vibration Response as Tools for Gearbox Diagnosis
Quick assessment of the condition of gearboxes used in helicopters is a safety requirement. One of the most widely used helicopter on-board-mounted condition monitoring system these days is the Health and Usage Monitoring System. It has been specifically designed to monitor the condition of all safety-critical components operating in the helicopter through calculation of so-called condition indicators (CIs) - signal processing routines designed to output a single number that represents the condition of the monitored component. Among number of available parameters, there is a couple of CIs that over the years of testing have earned a reputation of being the most reliable measures of the gear tooth condition. At the same time, however, it has been observed that in some cases, those techniques do not properly indicate the deteriorating condition with the propagation of a gear tooth fault with the period of operation. Hence, three more robust methods have been suggested, which are discussed in this article
Precision Electromagnetic Structure of Octet Baryons in the Chiral Regime
The electromagnetic properties of the baryon octet are calculated in quenched
QCD on a 20^3 x 40 lattice with a lattice spacing of 0.128 fm using the
fat-link irrelevant clover (FLIC) fermion action. FLIC fermions enable
simulations to be performed efficiently at quark masses as low as 300 MeV. By
combining FLIC fermions with an improved-conserved vector current, we ensure
that discretisation errors occur only at O(a^2) while maintaining current
conservation. Magnetic moments and electric and magnetic radii are extracted
from the electric and magnetic form factors for each individual quark sector.
From these, the corresponding baryon properties are constructed. Our results
are compared extensively with the predictions of quenched chiral perturbation
theory. We detect substantial curvature and environment sensitivity of the
quark contributions to electric charge radii and magnetic moments in the low
quark mass region. Furthermore, our quenched QCD simulation results are in
accord with the leading non-analytic behaviour of quenched chiral perturbation
theory, suggesting that the sum of higher-order terms makes only a small
contribution to chiral curvature.Comment: 29 pages, 33 figures, 20 table
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